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CONFIGURABLE QUANTUM NETWORKS FOR ADVANCED COMPUTING (CoQuNAC) Irfan Siddiqi Lawrence Berkeley National Laboratory Department of Physics, University of California, Berkeley Hartmut Hffner, Joel Moore, Dan Stamper-Kurn, Umesh Vazirni, Birgitta Whaley, John Wu ASCR Workshop: Quantum Computing for Science, February 17-18, 2015

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Cold Atoms Circuits Trapped Ions Lattice Models (solids) Long coherence Flexible architecture Access dynamics (open) Advanced Measurement Spin-Boson Models Access dynamics (closed) Couple to hybrids THE HARDWARE

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MODELING CORRELATED MATERIALS Chemical formula Structural information Simplified description of essentials: model Hamiltonian Emergent properties: superconductivity, magnetism,... Chemical intuition/ Phenomenology DFT and other pseudopotential methods Analytical theory Many-body approximations (DMRG, DMFT,...) a major need/growth area Exact diagonalization (if model Hamiltonian small)

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MEASURING CORRELATION FUNCTIONS Complete knowledge is unnecessary and impractical: storing/measuring all eigenvalues will be impossible. The most important physical quantities are usually n-point correlation functions, which are expectation values of n products of local operators. Example of 1-point correlation function: energy density Dynamical 2-point correlations: energy transport, conductivity, Can we combine a strong-correlation solver with existing computational chemistry to describe, the 2-point dynamical correlation function of energy, describing photosynthetic energy transfer?

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THE HAMILTONIAN LANDSCAPE Quantum Ising, Bose-Hubbard, Spin-Boson Fermi Hubbard at fractional doping Synthetic gauge fields, Relativistic theories Ising-like magnets Superfluidity Electron-phonon interactions Photosynthesis Superconductivity Spin liquids Solar water splitting Quantum chromodynamics QFT? Gravity? Development Time

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WEAK MEASUREMENTS: REAL-TIME QUANTUM TRACKING Vary Measurement Strength Local Measurement Nodes Extend to Many Qubit Systems

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A SUPERCONDUCTING QUBIT TRIMER Spectroscopy Bose-Hubbard Hamiltonian (interacting bosons on a lattice)

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USE ABSTRACTIONS TO: - encapsulate machine details - enable complex automation/calibration - permit arbitrary changes in hardware microwave generator pulse sequence ADC spin spin coupler spin measurement BEYOND THE SIMPLE CASES: HIGH LEVEL PROGRAMMING

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CHEMISTRY C ONFIGURABLE Q UANTUM N ETWORK N = 1 - 100 Trapped Ions Ultracold Atoms Superconducting Circuits Can control: (i) lattice size & topology (ii) Local spin state (iii) coupling (iv) measurement C ONFIGURABLE Q UANTUM N ETWORK N = 1 - 100 Trapped Ions Ultracold Atoms Superconducting Circuits Can control: (i) lattice size & topology (ii) Local spin state (iii) coupling (iv) measurement MATERIALS SCIENCE STAT/ THERMO COMPUTER SCIENCE STABILIZATION/ FEEDBACK MEASUREMENT VALIDATION (cf. classical) ADVANCED MATERIALS VERIFICATION ERRORS Configurable Quantum Networks for Advanced Computing (CoQuNAC)

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QUESTIONS OF INTEREST What types of Hamiltonia are accessible with CoQuNAC? Emulation versus simulation with gates? How does one program the simulation? (ie. map to Hamiltonian) What parts of the network need to be measured? How? How to protect against errors? How to define success/completion? How to compare to classical solvers? Benefits of quantum coherence? (cf. AQC, Annealing: Vazirani) How far can this technique be extended (resources/utility)? How do we serve the scientific community at large?